LNK2001: Unresolved External Symbol __chkesp (Visual Studio 6.0)

Problem: When linking a program compiled with Visual Studio 6.0, you get the following error message:

LNK2001: Unresolved External Symbol __chkesp

Explanation:
The compiler generates a call to a function to check for stack overflows. This function is not found in the C++ libraries you are linking with.

Solution:
Change your project settings to compile without stack checking. Select "Project | Settings | C/C++". Carefully check the Project Options window. Somewhere in there you should find the /GZ option. Remove it and recompile.

Further reading:
Microsoft Knowledge Base Article - 191669